This application claims benefit of Japanese Application No. 2000-164835 filed on Jun. 1, 2000, the contents of which are incorporated by this reference.
Field of the Invention and Description of the Related Art
The present invention relates to an ultrasonic probe including ultrasonic transducer to be used for ultrasonic observation.
Conventionally, resin such as polyethylene and polytetrafluoroethylene is used as a sheath material of a mechanical scanning type ultrasonic miniature probe. However, in an acoustic window portion of the sheath, which touches an object and allows ultrasound to pass through, the object and the sheath material have different acoustic impedances. Therefore, for example, the sensitivity (transmission coefficient) of ultrasound is reduced due to reflection of ultrasound occurred at the interface. Images are deteriorated due to multiple reflection at an interface. As a material for improving the acoustic matching, polyamide block and polyether ester block copolymer resin is disclosed in Japanese Examined Patent Application Publication No. 6-57211.
However, the flexibility of the polyamide block and polyether ester block copolymer resin disclosed in the Japanese Examined Patent Application Publication No. 6-57211 tends to decrease as the chemical resistance and the heat resistance increase. Therefore, when an ultrasonic miniature probe having a sheath of polyamide block and polyether ester block copolymer resin sheath with higher chemical resistance is inserted through an endoscope channel, the miniature probe may easily buckle due to steep bending of the endoscope.
It is an object of the present invention to provide an ultrasonic probe, which hardly buckles even when the ultrasonic probe is inserted through an endoscope channel or the like and which can reduce multiple reflection in the vicinity of an acoustic window.
It is another object of the present invention to provide an ultrasonic probe, which can reduce multiple reflection at least in the vicinity of an acoustic window.
There is provided an ultrasonic probe, including:
a long and narrow flexible sheath;
a cover member covering a hollow portion provided on a distal end side of the sheath in a liquid-tight manner;
an ultrasonic transducer, which is placed within the hollow portion covered by the cover member, for transmitting and receiving ultrasound;
an acoustic medium, which is filled around the ultrasonic transducer, for conducting ultrasound; and
an acoustic window portion, which faces against an transmitting and receiving surface for transmitting and receiving ultrasound of the ultrasonic transducer in the cover member and which is formed of a resin including a mixture of polyamide block and polyether ester block copolymers and polyurethane, for allowing ultrasound to pass through. Thus, the difference from the acoustic impedance of a living body can be reduced relatively. Therefore, the multiple reflection can be reduced. Furthermore, the sheath may also be formed of the resin. Thus, the sheath can be inserted into an endoscope channel without buckling.